I cannot really say whether it is necessary or not. To be on the safe side , yes. But, there's some catches with it; the 34L engine has the first XT600 oil pump, later models received +50% or +100% oil pumps. I have heard of a story of an older TT with the first model pump, where a cooler was installed. The cooler apparantely reduced the flow to the big end causing it to fail.
So, if you install a cooler, upgrade the engine with a +100% oil pump. This +100% pump has been installed as of the type number 3AJ, this number is also cast-in into it's housing. Another reason for doing this is that your oil pump is probably pretty worn by now.
As for coolers, anything goes. There's some nice ones with KEDO.com, I would think they also ship to Canada.